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Performance of available air-source heat pumps (ASHP) for buildings is extremely influenced by the outdoor air temperature (OAT). When OAT falls below –20 °C, especially in subarctic climate, most commercially available ASHPs lose their defined functionality. To address this issue, a novel cascade heat pump (CHP) is proposed that utilizes two natural (with zero global warming index) refrigerants: ammonia, aka R717, as the low stage (LS) refrigerant, and water, aka R718, as the high stage (HS) working fluid. The proposed system is equipped with two rotary vane compressors for LS and HS. To desuperheat the compressor discharge temperatures and increase the HS heating capacity, liquid refrigerant is injected into the chamber of both LS and HS compressors. The wet compression is thermodynamically modeled and validated against experimental data available in the literature. Optimum design parameters such as the maximum allowable temperatures during compression and the minimum vapor quality after injection are obtained where the COP is maximized. Total exergy destruction, number/location of injectors and the injected amounts are also investigated. The proposed CHP can deliver 6.35 kW heating load at 50 °C with a COP of 1.985 when OAT is –40 °C. From a broader perspective, the proposed CHP not only proves its efficacy in extremely cold subarctic climates but also emerges as a pivotal player in addressing the global warming issue. This is accomplished through a dual approach to decarbonization—firstly, by electrifying heating processes and secondly, by substituting phased-out refrigerants with environmentally friendly natural alternatives. [ABSTRACT FROM AUTHOR]

A novel CO 2 air-source heat pump system (ASHPs) with a secondary throttling based on a single-stage compression was proposed to further improve the heating energy efficiency of electric vehicles (EVs) for heating in cold climates. The heating characteristics of the secondary throttling system (STS) and conventional throttling system (CTS) at different indoor air supply temperatures were compared. The STS performance characteristics were investigated under varying ambient temperature, outdoor air velocity, and exergy analysis was performed on the system and its components. A fitting correlation equation for optimal discharge pressure was obtained based on experimental data. The results demonstrate that implementing STS significantly reduces CO 2 ASHPs energy consumption (W com), enhances the coefficient of performance (COP), and reduces exergy destruction. When the indoor air supply temperature reaches 45 °C, using STS can result in an 8.1 % reduction in W com , a 9.4 % increase in COP, and a 6.1 % improvement in the exergy efficiency (Ex η) compared to that of CTS. Furthermore, the advantages of STS become more pronounced with higher indoor target air supply temperatures. As the ambient temperature decreases, the exergy efficiency of the STS reaching the target air supply temperature decreases. The velocity of outdoor air significantly affects the STS performance, and increasing outdoor air velocity can effectively enhance the Ex η of STS. The optimal discharge pressure fitting equation for the STS was obtained through multiple linear regression analysis. These findings can provide ideas for architectural optimization and design of CO 2 ASHPs for EVs, which are important for further improving system performance. [ABSTRACT FROM AUTHOR]

Individual heating systems, such as the air-source heat pump (ASHP) air-conditioner or floor heating (FH), are usually used by people living in the hot summer and cold winter (HSCW) zone of China to heat indoor climates in the winter. However, little research has been conducted in the HSCW zone on the thermal comfort difference between indoor climates heated by ASHP air-conditioners and those heated by floor heating, as well as how occupants adapt to different indoor climates. We conducted a comparative field experiment in ASHP-heated and FH-heated apartments in Nanjing to investigate how different types of heating systems influence the thermal sensation of occupants, and we conducted a comparative field experiment in ASHP-heated office buildings and naturally ventilated teaching buildings in Shanghai to investigate how occupants adapt to different indoor thermal environments. Indoor environmental parameters and body surface temperatures were measured using instruments, and occupants' thermal sensation, activity level, and clothing were evaluated using the questionnaire. The results show that floor heating improves thermal comfort by raising foot temperature compared to the ASHP air-conditioner, and that occupants become acclimatized to different indoor climates by adjusting neutral operative temperature. According to the findings, there is no need to overheat the indoor environment in the HSCW zone because occupants can adapt to their experienced thermal environment and it is critical to maintain warm foot temperature in the cool/cold indoor environment. [ABSTRACT FROM AUTHOR]

Air-source heat pumps (ASHPs), as an active device, are widely used in building heating and cooling processes. However, in severe cold regions, they face reduced heating efficiency and frosting problems in winter. This paper proposes a new heating solution by coupling an ASHP with passive heating systems. It combines an ASHP with passive sunrooms and heat storage systems for heating. Through software simulations and mathematical modeling, the new scheme is compared and analyzed against traditional ASHP solutions to explore the performance of this scheme in rural houses in severe cold regions of China during winter. According to simulation and calculation analysis, on the coldest day of winter, the coupling scheme can provide approximately 99.41 kWh of heat to the indoors, which exceeds the 86.67 kWh required to maintain an indoor temperature of 20 °C. The system's power consumption is 36.96 kWh, which is 66.88% lower than that of traditional heat pump heating. The study shows that the coupling system of an ASHP and passive heating has a good heating effect in severe cold regions. For the situation of insufficient solar energy at night, the design of phase-change materials and heat storage media can meet heating needs throughout the day. [ABSTRACT FROM AUTHOR]

The efficiency and economy of an ASHP (air source heat pump) can be significantly improved in a cold area by combining it with a TESU (thermal energy storage unit). The work of looking for a phase change material with a suitable temperature range, a large thermal capacity, and high conductivity has been always on the road. This paper prepared 10 CPCMs (composites of a phase change material) by using the vacuum adsorption method, which consists of LA (lauric acid) as the phase change material and EG (expanded graphite) as the skeleton matrix for its high thermal conductivity and porous characteristics. By characterizing and analyzing their basic properties, surface morp\hology, and stability, a suitable CPCM for the TESU coupled with the ASHP heating system is found. The leakage experiment results show that the maximum effective content of LA absorbed in 100-mesh EG of a CPCM is 80%, and that in 200-mesh EG, it is 90%. Among 10 CPCMs, CPCM3, with a mass ratio of LA:EG/8:2, is considered the more satisfactory one for the TESU proposed by this paper, because its performance shows good stability, its phase transition temperature is 40.98–41.94 °C, its latent heat is 164.34–168.28 kJ/kg, and especially, its thermal conductivity is 8.15–8.33 W/(m·K). This paper will be followed by performance research on TESUs coupled with ASHP heating systems. [ABSTRACT FROM AUTHOR]

The escalating energy demands in buildings, particularly for heating and cooling demands met by heat pumps, have placed a growing stress on energy resources. The bi-functional thermal diode tank (BTDT) is proposed as thermal energy storage to improve the heating and cooling performances of heat pumps in both summer and winter. The BTDT is an insulated water tank with a gravity heat pipe (GHP), which can harvest and store heat passively from sun radiation and the external environment during the daytime. In summer, it harvests and stores cold energy from the air and night sky during the daytime. The performance of the BTDT-assisted heat pump (BTDT-HP) system in Adelaide, Australia, during the 2021–2022 summer and winter seasons was evaluated by conducting a TRNSYS simulation. This study revealed that the BTDT-HP system outperformed the reference ASHP system, where up to 8% energy in heating and 39.75% energy in cooling could be saved. An overall reduction in the energy consumption of 18.89% was achieved. Increasing the BTDT volume and GHP panel area enabled the tank to store more thermal and cold energy across the winter and summer seasons, thereby improving the system's performance. The maximum ESPs were found to be 31.6% and 41.2% for heating and cooling for the study case under optimal conditions. When the GHP panel area was fixed at 15 m2, the BTDT volume should be at least 28 m3 for the BTDT-HP system, boasting cooling and heating capacities of 40 kW and 43.2 kW, to achieve positive energy savings. [ABSTRACT FROM AUTHOR]

Clean heating transformation and photovoltaic (PV) promotion gradually have become the keys to realize dual carbon strategy goals. Based on this, the combined application of building-integrated PV (BIPV) systems and air-source heat pump (ASHP) systems has received widespread attention. However, the current combined system still presents problems such as the mismatching in time between PV output and heating load. Therefore, in this paper, a novel BIPV and ASHP coupling system is proposed, and the operation parameters were optimized using low-carbon community as an example. A conventional PV and heat pump (HP) combined system, ASHP heating, and coal-fired heating were employed as the baseline and compared with the novel system. The results show that the optimized system can improve the PV power local accommodation rate by 43% compared with a conventional PV and ASHP coupling system. In terms of economic and environmental benefits, the operating cost of the optimized system is 50% of the cost of the ASHP system. Compared with coal-fired heating system, the annual air pollutant and carbon emissions can be reduced by 92% and 57%, respectively. The system also can improve the stability of power grid operation. The demand for power capacity can be improved by 62% and the annual load balance of the power grid can be improved by 29.5%. [ABSTRACT FROM AUTHOR]

The widespread adoption of air source heat pumps (ASHP) in energy-saving building projects can be attributed to their mature technology, high efficiency, and environmentally friendly characteristics. However, the impact of various locations of water storage tanks on the performance of ASHP utilizing CO2 as the working fluid for space heating is rarely reported in in existing literature. Therefore, this study aims to investigate the heating characteristics of three CO2 ASHP systems with varying water tank locations using TRNSYS software. The heating performance of these systems are evaluated based on key parameters such as coefficient of performance (COP), energy consumption, economic viability, and emissions including CO2, SO2 and dust etc. The findings reveal that system A exhibits the highest annual average COP at 2.87, followed by system C at 2.61 and system B at 2.46. Furthermore, in terms of total cost over the entire heating period, system A demonstrates a significant advantage with a value of 3334.2 CNY which is 56.9 % lower than system B and 24 % lower than system C respectively. [ABSTRACT FROM AUTHOR]

Air-source heat pumps (ASHPs), functioning as thermally controlled loads, possess significant adjustable capabilities and controllability when aggregated, establishing them as premium resources for demand-response engagement. This paper proposes a control strategy for the aggregation of ASHP loads to participate in demand response across multiple scenarios, framed within a three-tier architecture: electric power system, Load Aggregator (LA), and thermal load. Load Aggregators, considering the user-comfort temperature ranges and the thermal storage characteristics of buildings, aim to minimize heating costs through time-of-use electricity pricing, while assessing the adjustability of the load. Upon receiving control directives from the power system's dispatch department, the strategy allocates load adjustments by considering user comfort and system regulatory needs, thereby addressing issues like aggregated power oscillations and significant rebound loads. The effectiveness of the proposed strategy is corroborated through simulation, demonstrating its potential to enhance demand-response participation and ameliorate associated power stability challenges. [ABSTRACT FROM AUTHOR]

To enable net zero sustainable thermal building energy, this study develops an open-source thermal house model to couple solar photovoltaic (PV) and heat pumps (HPs) for grid-connected residential housing. The calculation of both space heating and cooling thermal loads and the selection of HP is accomplished with a validated Python model for air-source heat pumps. The capacity of PV required to supply the HPs is calculated using a System Advisor Model integrated Python model. Self-sufficiency and self-consumption of PV and the energy imported/exported to the grid for a case study are provided, which shows that simulations based on the monthly load profile have a significant reduction of 43% for energy sent to/from the grid compared to the detailed hourly simulation and an increase from 30% to 60% for self-consumption and self-sufficiency. These results show the importance of more granular modeling and also indicate mismatches of PV generation and HP load based on hourly simulation datasets. The back-calculation PV sizing algorithm combined with HP and thermal loads presented in this study exhibited robust performance. The results indicate this approach can be used to accelerate the solar electrification of heating and cooling to offset the use of fossil fuels in northern climates. [ABSTRACT FROM AUTHOR]

Drying agricultural produce consumes a considerable amount of energy. As an energy-efficient system, a heat pump can improve the energy efficiency of the drying process and hence reduce the energy consumption, especially in South Africa, where both sub-tropical and temperate weather conditions dominate. The objective of this research is to experimentally investigate the impacts of weather conditions on the operational conditions and thermal performance of an open-loop air-source heat pump drying system. The experimental investigation was conducted in a climate chamber where the climate conditions were simulated from −10 °C to 20 °C with an interval of 10 °C for the typical temperature range of the harvesting season in South Africa. The findings indicate that ambient temperatures have a significant impact on both the operating conditions and thermal performance of an open-loop heat pump system; the change in ambient temperatures from −10 °C to 20 °C leads to a 141.6% improvement in the suction pressure, a 214.2% increase in the discharge pressure, and 30.1% increase in the compression ratio, as well as a consequent increase of 130.6% in the refrigerant mass flow rate (from 0.0067 to 0.0155 kg/s), resulting in a corresponding increase in the coefficient of performance (COP) of the heat pump drying system by about 42.1%. Therefore, this study suggests that, while using an open-loop air-source heat pump drying system utilising R134a refrigerant is feasible in South Africa, it may be practically limited to regions with warm climates or during warmer seasons. [ABSTRACT FROM AUTHOR]

Based on air-, water-, and ground-source heat pump systems, a novel type of heat pump system, named the heat-source tower heat pump system (HSTHPS), has recently been developed in the southern area of China. The HSTHPS overcomes the evaporator frosting problems of the air-source heat pump system (ASHPS) when the ambient temperature is lower, and it avoids the geological condition constraints of the water- and ground-source heat pump systems. However, studies on the HSTHPS are insufficient, thereby limiting its development and applications. Thus, the present review provides a detailed literature review on the advancements of HSTHPSs in China, including the HSTHPS operation principle, heat-source tower (HST) structure, heat and mass transfer characteristics, HSTHPS performance, antifreeze solution use, and antifreeze solution regeneration. Studies on the heat and mass transfer characteristics of HSTs are sufficient for guiding the application. Regarding open systems, the solution drifting to the air needs to resolved, and future studies need to focus on structure optimization for heat exchangers in closed systems. Moreover, advanced defrosting technology should be applied to closed-type HSTs, and a suitable operation strategy for HSTHPSs should be developed. Future priorities should involve integrating HSTHPSs with additional renewable energy in order to achieve continuous, stable, and efficient heating in winter based on the characteristics of local climate and renewable energy. [ABSTRACT FROM AUTHOR]

Existing research on the analysis heat pump operation generally focuses on the efficiency of doing work while ignores heat loss in the transfer process. Hence, heat pumps are often studied based on theory of minimum entropy production. However, this theory is rarely applied to optimizing heat transfer process without heat work conversion. Taking the air source heat pump hot water supply system of a hotel building as an example, this paper simulates the heat production, power and COP of the air source heat pump during operation based on the theory of entransy and entransy dissipation proposed by Professor Zengyuan Guo. The findings show that heat pump operates best at inlet water temperatures of 293 K and 298 K, with a COP of 4.8. In the water at a temperature of 298 K, water temperature can be adjusted by the function of heating capacity between 30 kW and 40 kW to minimize the system's entransy dissipation, where the system's unit power consumption reaches its minimum at 9 kW, corresponding to an entransy dissipation of 245.4 kJK. This study provides a good research idea to optimize the thermal power conversion process using the theory of entransy and entransy dissipation. [ABSTRACT FROM AUTHOR]

Refrigerant injection techniques are usually proposed to improve the performance and reliability of compressors when a single-screw compressor applied to an air-source heat pump works at low temperatures in winter. In this study, an experimental study was conducted to present the performance comparison of the single-screw compressor in the air-source heat pump under liquid, vapor, and liquid–vapor refrigerant injection at evaporation temperatures between −19 and −8 °C. The results indicate that, when the evaporation temperature decreases from −8 to −19 °C, the heating capacity under liquid–vapor and vapor injection increases by 16.7% and 12.7%, respectively, compared with that under liquid injection and that the COPh increment under liquid–vapor injection and vapor injection is, respectively, from 11.23% to 39.21% and from 17.18% to 30.82% compared with that under liquid injection. Therefore, the liquid–vapor injection method is conducive to the operation of the air-source heat pump at a lower ambient temperature. The experimental results can provide the basis for the future design of single-screw compressors applied to air-source heat pumps. [ABSTRACT FROM AUTHOR]

In the rural areas of Northwest China, the utilization of clean and renewable energy is deemed a crucial measure for reducing building energy consumption and environmental pollutant emissions. This paper focuses on constructing a simulation platform for a solar-assisted air source heat pump heating system. A rural residential building in Yongshou County, Shaanxi Province, serves as an illustrative example. A novel flexible temperature control method with a feedback controller in sub-area and period is proposed in this paper, alongside the selection of three distinct objective functions aimed at optimizing the heating system. The simulation results indicate an average temperature of 17.0 °C throughout the heating cycle, with a peak temperature of 18.7 °C. Moreover, the solar fraction is measured at 25.11%, underscoring the significance of collector area and heat storage tank volume as primary factors in system design. The results also demonstrate that across various optimization objectives, the life cycle cost optimization scheme yields greater economic benefits, while the target building unit heating cost optimization scheme boasts the shortest static payback period and lowest unit heating cost. Conversely, the solar fraction optimization scheme stands out for its superior environmental benefits. These findings offer valuable insights for the design of heating systems tailored to diverse objectives. [ABSTRACT FROM AUTHOR]

Combining various sources to create a complementary system plays a key role in utilizing clean energy sources economically and mitigating air pollution during the heating season in Northern China. However, there is a lack of unified and reasonable design methods for such systems, resulting in the excessive capacity of equipment and the waste of energy. In this work, a unified design method is proposed to solve this problem. A generalized structure and its mathematical model are firstly established, enabling transient simulations on the TRNSYS platform. Then, a preliminary screening criterion for the system composition a general operation strategy is proposed. Finally, the system configuration is optimized by using the genetic algorithm. The method is successfully applied in a demonstration project in China. The results show that the coupling system consisting of a biomass boiler (384 kW), an air-source heat pump (430 kW) and a ground-source heat pump (369 kW) is the most economical, and the annual cost is 26.7% lower than that of a single-equipment system. Additionally, the sensitive factors that strongly affect the optimization results are explored. The establishment of the generalized structure and its mathematical model enables the quick calculation and convenient comparison of various schemes, and simplifies the complicated optimization problem of the capacity optimization of each piece of equipment. The proposed design method can reduce the annual cost to a minimum value, and thus it provides a theoretical basis for the large-scale application of clean energy sources for heating. [ABSTRACT FROM AUTHOR]

The data obtained from a heating and cooling system comprised of a fan coil unit integrated air source heat pump used in Istanbul, Turkey, as well as data on outdoor conditions, was analyzed in this study. The analysis was carried out with the help of the moderated mediation model, which is included as a process analysis in the "Statistical Package for the Social Sciences" application. In this study, a mathematical model of the moderated mediation model was created and the efficiency coefficients of the parameters effecting performance were calculated. It was discovered that the effect of medium and high relative humidity values on the outdoor temperature was about 4.81%. The heat pump fails to transmit heat to the environment outside as a result of medium and high relative humidity values increasing the outdoor temperature. As a result of this it has been found that relative humidity values have a negative effect on the water temperature entering the fan coil unit by approximately -1.18%. This result of the study shows that the outlet water temperature of the fan coil unit does not adequately cool the rooms in the summer. It has been discovered that while wind velocity negatively affects performance affecting parameters, low relative humidity values have no effect on them. [ABSTRACT FROM AUTHOR]

In order to understand the process of using the heat pump heat organization, the author proposes to conduct a study based on the concept of heat pump air heating system in "Land Port Logistics Park". The author first analyzed the heating characteristics of the ground transportation fleet according to the actual situation, optimized the design of the heat pump, and proposed the same plan. Second, taking some provincial underground parks as examples, the actual performance of the park's air source heat pump heating system was tested. According to the test, the temperature difference between the supply and return water is 3-4 °C, and the average COP of the entire heating season is only 2.1. Based on the analysis and analysis, the meaning of the problem in the actual operation of the heat pump is explained, the cause of the problem is the determination of the pressure and the design plan. After installation, energy consumption can be further reduced, and it advises on the progress and use of the ventilation system. By using electric equipment to heat the docks in the port, it is possible to meet the heating needs of the park and reduce energy consumption and air pollution. Good this is a green and low carbon promise. [ABSTRACT FROM AUTHOR]

In recent years, due to the global energy crisis, the idea of a photovoltaic-assisted air-source heat pump (PV-ASHP) has become increasingly popular. This study provides a simulation in TRNSYS and the analysis of the use of a PV-ASHP system in a service building in different climate zones of Poland. For each of the six cities—Kolobrzeg, Poznan, Krakow, Warsaw, Mikolajki, and Suwalki, the effect of changing five system parameters (area, efficiency, type, and location of photovoltaic panels, and the use of a heat pump control strategy) on the amount of energy generated and consumed was determined. We also estimated the extent to which the photovoltaic panels could cover the energy requirements for the heat pump (HP) operation and the system could provide thermal comfort in the service room. Finally, a simplified analysis of the operating costs and capital expenditures was made. The results highlighted the issue of the incoherence of renewable energy sources and the need to store surplus energy under Polish climatic conditions. Abandoning the HP control strategy increased energy consumption by 36–62%, depending on the location and Variant, while the change in the place of the PV panels on the roof slope reduced energy generation by 16–22%. When applied to an ASHP in a service building, the use of PV panels to power it seems to be cost-effective. [ABSTRACT FROM AUTHOR]

To determine the optimal heating method for gymnasiums, this study focuses on a specific gymnasium. The heat load of the gymnasium is analyzed by importing the meteorological data of Xi'an, and energy consumption simulation models for four heating systems are developed using the TRNSYS simulation software. The economic evaluation of these systems is conducted using the annual cost value method, and the optimal solar collector area is proposed. Additionally, the study examines the impact of different electricity prices on the annual cost value of the heating systems, as well as the optimal heating system configuration and its effect on the annual cost value under varying electricity prices. The main conclusions are as follows: (1) The density of people in the competition hall is much higher than that in the practice area, and the competition hall is located in the inner area with no external heat transfer protection structure, only the roof is used for heat exchange. The heat load in the competition hall (14.43 W/m2) is lower than that in the practice area (81.41 W/m2); (2) Through the economic analysis of two solar composite heating systems with different heat collection areas. The optimal heat collection area of the solar coupled electric boiler system and the solar coupled air source heat pump are 3024 and 2394 m2, respectively, and the minimum annual cost are 1,132,300 and 699,200 CNY, respectively; and (3) An economic analysis is conducted on the four heating systems at different electricity prices. When the electricity price is between 0.5 and 1.0 CNY/kWh, the air-source heat pump coupled with electric boiler system has the lowest annual cost value. However, when the electricity price is between 1.1 and 1.5 CNY/kWh, the solar energy coupled with air-source heat pump system has the lowest annual cost value. [ABSTRACT FROM AUTHOR]

Temperature control with conserving nutrients and irrigation water reduces energy loss, leading to economic and sustainable greenhouse farming. A subirrigation system was applied to strawberry cultivation by placing tubes containing temperature-controlled water (obtained using heat pumps with air or geothermal heat sources) under the soilless substrate of a cultivation container. A ball tap supplied water gravitationally, avoiding the need for a water reservoir, thereby minimizing the volume of water required for heating and cooling. The substrate temperature in the heat pump treatments retained an optimal temperature for growth (averaging 18.4 ℃ in all seasons). The coefficient of performance of the heat pump with the geothermal heat source during heating operations was approximately 1.8 times higher than that with the air heat source. However, the geothermal heat source reduced overall electricity consumption by 14.9% for five months of the experimental period. Production was increased by 21% and 36% in the geothermal and air-source heat pump treatments, respectively, compared to that of the control, owing to the preferable condition of the substrate for strawberry growth. Although salinization of the substrate due to the closed irrigation system may be of concern and damage plant growth, the subirrigation system minimized the loss of water, nutrients, and heat owing to the omission of a reservoir. Furthermore, with minor modifications, the proposed system could be converted to a dual heat pump system to enhance energy use efficiency. [ABSTRACT FROM AUTHOR]

In the context of global climate change, the implementation of building energy conservation and carbon reduction, as well as the realization of zero-energy buildings, is a key measure to cope with climate change and resource depletion. A substation is an indispensable building in the process of urbanization construction. However, in existing cold areas, the heating form of substations generally adopts electric heating, which consumes a large amount of energy. This paper optimizes the existing HVAC form of substations through the rational utilization of surrounding environmental resources and puts forward reasonable building energy-saving and carbon-reduction methods. It demonstrates the feasibility of combining solar photovoltaic power generation systems, air source heat pumps, and natural ventilation to optimize energy savings and carbon reduction in the main control building of a substation in a cold area. The computational fluid dynamics (CFD) method is used to demonstrate the feasibility of natural ventilation during the summer and transition seasons. The data indicate that the installation of a solar photovoltaic power generation system results in an average annual power generation of 18.75 MWh. Additionally, using an air source heat pump can save 44.5% of electricity compared to electric heating. When both a solar photovoltaic power generation system and an air source heat pump are used to provide a building with cold and heat sources, the annual emissions of CO2 can be reduced by 4.90 tons compared to a traditional electric heating system. [ABSTRACT FROM AUTHOR]

Building heating is an indispensable part of people's winter life in cold regions, but energy conservation and emission reduction should also be taken into account during the heating process. This paper provides a concise overview of the heating system based on air-source heat pump radiant floor and its control strategy. It also optimizes a control system based on thermal comfort and energy efficiency ratio, and analyzes a room in Xining City, Qinghai Province, to test the heating system performance under two control strategies. The final results show that under the traditional control strategy, the cumulative working time of the heating system within a day was 15 hours, the average indoor temperature was 17.36°C, the temperature standard deviation was 2.08°C, and the average power consumption was 189.6 kWh. Under the improved control strategy, the cumulative working time of the heating system within a day was reduced to 10 hours, the average indoor temperature was 18.56°C, the temperature standard deviation was 0.92°C, and the average power consumption was 132.5 kWh. [ABSTRACT FROM AUTHOR]

To achieve the goal of carbon peaking, it is crucial to reduce both carbon emissions and energy consumption during the operational stage of residential buildings. This paper proposed a method for assessing carbon emissions and energy consumption for an energy system utilized in a rural residence. First, an equivalent thermal resistance-capacitance model for a rural residence was established. The parameters of thermal resistance and capacitance were optimized based on the data collected from an operating air source heat pump heating system. On this basis, the energy consumption was derived, and it was compared with real consumption. Then, a method of estimating house energy consumption index per unit area under specified weather conditions was proposed. Finally, the carbon emissions of three heating types—heating driven by air source heat pump, gas boiler, and coal boiler—were compared. Results showed that the derived energy consumption index per unit area was 46.77 W/m2. The carbon emissions of the air source heat pump were 1406.1 kgCO2. [ABSTRACT FROM AUTHOR]

• Higher initial compressor temperature results in higher minimum viscosity. • Refrigerant concentration gradient went from present to absent during startup. • Poorer miscible lubricant results in higher mixture viscosity. • Oil discharge originates from excessive refrigerant condensation and oil supply. • PAG VG40 and MO VG100 showed good oil return performance. The low density, small adiabatic index, and restricted charge of R290 result in different startup characteristics for R290 air-source heat pumps (ASHP) from that for HFCs ASHP. The research on the startup process of R290 refrigeration systems in the past has focused on system and compressor pressures, temperatures, changes in the bottom viscosity of the oil sump, and control strategies. There is a lack of research on the effect of lubricant types on the startup process, especially for R290 air-source heat pump. This paper experimentally measured and analyzed the changes in system temperatures and pressures as well as the changes in refrigerant concentration, concentration gradient, and mixture viscosity in the compressor oil sump during the startup process of R290 ASHP under different conditions, different startup types and with different lubricants. In addition, the oil discharge time, oil discharge, refrigerant mass in the compressor, and oil return time during the cold startup of LTH using PAG VG40 and MO VG100 were observed and clarified by installing transparent tubes and dismantling and weighing method. The experimental results showed that during the startup process, the mixture viscosity in the oil sump decreased and then increased, the refrigerant concentration increased and then reduced, and the refrigerant concentration gradient went from present to absent. The minimum viscosity was greater, the maximum concentration was smaller, and the low-viscosity duration was shorter for higher initial compressor temperature and with poorer miscible lubricants. PAG VG40 and MO VG100 showed good oil return performance. [ABSTRACT FROM AUTHOR]

This paper combines the advantages of air source heat pumps and proton exchange membrane fuel cells, and analyses the dynamic performance, environmental benefits, and economic benefits of combined cooling, heating, and power (CCHP) systems combined with energy storage systems applied to residential buildings. The fuel cell voltage and heat model, air source heat pump (ASHP) model, and energy storage system model are developed in MATLAB. The results show that the problem of thermoelectric asynchrony and excess energy wastage can be solved by using the heat-following strategy with a battery and the electric-following strategy with a water tank. With the heat-following strategy in winter, the total thermodynamic efficiency of the system is 1.265, the carbon emission reduction is 6208.6 g, and the initial cost, operation cost, and maintenance cost are 6007$, 11.99$, and 300.35$, respectively. The efficiency of the system with the winter electric-following strategy is 1.284, the emission reduction is 6781.4 g, and the initial cost, operation cost, and maintenance cost are 7202.9$, 11.88$, and 360.14$, respectively. In summer with the electric-following strategy, the thermodynamic efficiency of the system is 1.514; the carbon reduction is 8,033.6 g. The initial cost, operation cost, and maintenance cost are 7,208.3$, 14.84$, and 360.42$. [ABSTRACT FROM AUTHOR]

To enhance system stability, solar collectors have been integrated with air-source heat pumps. This integration facilitates the concurrent utilization of solar and air as energy sources for the system, leading to an improvement in the system's heat generation coefficient, overall efficiency, and stability. In this study, we focus on a residential building located in Lhasa as the target for heating purposes. Initially, we simulate and analyze a solar-air source heat pump combined heating system. Subsequently, while ensuring the system meets user requirements, we examine the influence of solar collector installation angles and collector area on the performance of the solar-air source heat pump dual heating system. Through this analysis, we determine the optimal installation angle and collector area to optimize system performance. [ABSTRACT FROM AUTHOR]

All the modern gadgets and space conditioning in buildings consume lots of energy. Energy consumption can be optimized using Composite Insulation External Walls (CIEW) built from mortar plaster and structural and insulation layers. This study aimed to improve the overall performance of CIEW by optimizing the structural and insulation layer thickness. The objective was to minimize the Life Cycle Cost (LCC) and maximize the Life Cycle Savings (LCS) of CIEW. The nonlinear Least Squares Estimation (LSE) optimization technique for optimizing LCC and LCS of CIEW was used in the study. The study considered three insulation materials—Extruded Polystyrene (XPS), Rock Wool (RW), and Glass Wool (GW)—across three heat sources, including Circulating Fluidized Bed (CFB), Grate-Fired Boiler (GFB), and Air-Source Heat Pump (ASHP). The Life Cycle Cost Analysis (LCCA) methodology suggested by Huang using a traditional optimization technique was used as a basis for mathematical formulations and result comparison. The payback period of CIEW with optimal structural and insulation layer thickness was computed. The findings revealed that applying the LSE method enabled greater economic efficiency than the LCCA method, with an up to 9.12% increase in LCS value and an up to 7.41% decrease in LCC value. The research also revealed significant correlations between insulation and structural layer thicknesses and economic parameters. [ABSTRACT FROM AUTHOR]

The UK government has legal binding objectives under the "climate change act 2008" to accomplish net-zero carbon emissions by the year 2050. The government has implemented a variety of measures across many different sectors of the UK economy that are accountable for the emissions. The aim of this research was to evaluate and compare some existing renewable energy technologies. It discusses the advantages and disadvantages of installing these technologies into homes across the UK and the impact it has on the "net-zero housing" scheme. A series of results were produced using the SAP rating, deploying an existing dwelling located in Bradford, UK, fitted with a gas boiler and comparing the results to those obtained for an air source heat pump (ASHP) and a mechanical ventilation with heat recovery system (MVHR). The three systems were analysed in terms of cost-effectiveness, carbon footprint and energy savings. The study found that the installation of a gas boiler costs less than that of the other systems, whilst ASHPs involve high upfront costs. However, the latter showed higher energy savings, with an efficiency of 4.0 compared to 0.75 and 0.95 for the gas boiler and MVHR, respectively. The SAP rating showed that the ASHP had a carbon footprint of 2396.3 kg/year for the studied flat of 65.72 m2, whilst carbon footprints of 3406.92 CO2 kg/year and 7143.45 kg/year were determined for the gas boiler and the MVHR system, respectively. The study concluded that ASHPs work better than the other systems for most of the existing UK housing, unless a whole building fabric improvement is considered, in which case, some other renewable options could be a choice. [ABSTRACT FROM AUTHOR]

Hybrid heat pump (HHP) represents a heating system (HS) that simultaneously utilises two or more energy sources. The key novelty is the integration of an optimised control strategy, effectively maximising the efficiency of both the heat pump and gas boiler segments. In this study, a HHP system that consists of an air-source heat pump (ASHP) and a condensing-type gas boiler (GB) for a two-story single-family house was calculated and validated. The results from three different calculation methods were obtained: the heat pump manufacturer's calculator, the simulator programme, and the calculations based on real measured data. Two operation modes were tested: economic mode, where the cheapest energy resource becomes the priority, and ecological mode, where the system operates using the energy resource with lowest CO2 emissions. When comparing consumed energy, there was a 15.36% variance between the manufacturer's program and the actual measured data, while for produced energy, the difference amounted to 25.81%. It was found that the balance point temperature is −7 °C, where the heat pump unit of the HHP system can cover necessary heat losses until that point, while the gas boiler operates at lower temperatures. Changes in electricity price can significantly influence the point of the system switch, but the possibility to cover heat loads of the heat pump unit always has to be taken into account. [ABSTRACT FROM AUTHOR]

Solar application in buildings is limited by available installation areas. The performance of photovoltaic (PV) and solar collectors are compared in meeting the heating and cooling demand of a residential house using 100% solar energy through TRNSYS modelling of five systems that use air source heat pump and seasonal energy storage as optional assisting technologies. The results show that in a large scale, the PV working with air source heat pump is more efficient than the solar collector system. However, the photovoltaic/thermal (PV/T) is the most spatially efficient with an energy capacity of 551 kWh/m2, 10.6% higher than that of the PV. Compared with the air source heat pump heating system using grid power, using solar energy regardless of system formats can reduce emission by 72% in a lifetime of 20 years. Solar energy can become cost-effective if the utility price is increased to above 0.7 CNY/kWh. The results can help in renewable planning in the studied climate. [ABSTRACT FROM AUTHOR]

Heat pumps offer an efficient electrification of space heating but can significantly vary the magnitude and duration of house-level electrical demand, especially when replacing fuel-fired heating systems. This paper uses a simulation-based approach to simulate the electrical demand variations of air-source heat pumps (ASHPs) in six Canadian cities (Halifax, Montreal, Toronto, Winnipeg, Vancouver, Whitehorse) when replacing natural gas or electric baseboard heating. Detailed housing models (including a highly zoned model capturing room-based baseboard controls) are combined with a series of custom non-HVAC load profiles and an enhanced data-driven ASHP model to assess the variation that occupancy, climate, and type of heat pump integration can have on electrical demand. ASHPs are shown to increase the magnitude and duration of electrical demand when replacing natural gas furnaces, although selection of climate-appropriate systems (e.g. cold climate units in colder climates) may reduce the magnitude and coincidence of this demand. Where heat pumps replace electric baseboards, HVAC demand may decrease by up to 3.4 kW during ASHP operating periods and remain equal when the ambient temperatures are below the ASHP cutoff. A study of simple mitigation measures through varying temperature setpoints demonstrates the ability of proper controls to reduce electrical demand during high-demand periods. [ABSTRACT FROM AUTHOR]

In the last decade, due to climate change concerns and new environmental regulations in the EU, there was a tremendous rise in installed heat pump systems in new homes and buildings. The majority of these installed units are related to air-source heat pumps, as they offer a good trade-off between capital and operating expenses. However, when analysing heating and cooling heat pump systems from the primary energy consumption and ecological aspects, groundwater and shallow geothermal heat pump systems offer superior efficiency, compared to all market-available thermo-technical systems today. In the last decade, ground-source systems have seen some technological improvement by employing new borehole heat exchanger designs, such as piping with internal fins and a wider diameter (so called Turbocollector) to enhance the heat transfer between fluid and rock, as well as to reduce the pressure drop in the system. Furthermore, the process of drilling deeper offers higher ground temperatures and consequently higher seasonal performance factors in the heating cycle, due to the effect of the geothermal gradient. Nevertheless, although deeper boreholes provide better heat extraction rates per meter during the heat pump heating cycle, at the same time, it reduces heat rejection rates during the heat pump cooling cycle. The objective of this paper is to analyse and evaluate benefits and downsides of a new approach in the heat pump system design with deeper borehole heat exchangers of up to 300 m, comparing it to the traditional design of double-loop exchangers with 100 m depth. The geothermal borehole grid design simulation model, along with heat extraction and rejection, is performed on a yearly basis. The results are showing that the benefits of shallow geothermal boreholes, from the hydraulic and thermodynamic point of view, still dominate over deeper solutions. [ABSTRACT FROM AUTHOR]